Traffic engineering is about optimization of general performance of a network. It aims to provide efficient and reliable network services conveniently, optimize utilization of network resources, and optimize network traffic. Path computation is an important part of the Multi Protocol Label Switch (MPLS) and the General Multi Protocol Label Switch (GMPLS).
In traffic engineering, a Path Computation Client (PCC) generally needs to obtain the shortest path between the source node and the destination node. The source node and the destination node are generally not in the domain covered by one PCE. The domain covered by a PCE may be one of multiple domains in an autonomous system, or may be an autonomous system. FIG. 1 shows PCE network architecture. In FIG. 1, a PCE is responsible for path computation and management of an autonomous system. PCE 1 is responsible for autonomous system 1, PCE 2 is responsible for autonomous system 2, and PCE 3 is responsible for autonomous system 3. Each PCE stores the topological connection relations of all PCEs in the network. When the source node in the autonomous system 1 needs to obtain the shortest path from the source node to the destination node, the method of obtaining the shortest path includes the following steps:
The source node uses itself as a PCC to send a path computation request to PCE 1. PCE 1 generates a PCE sequence from PCE 1 to the destination node according to the topological connection information stored in PCE 1, and sets up a Path Computation Element Protocol (PCEP) connection between PCE 1 and the PCE corresponding to the destination node according to the PCE sequence. PCE 1 transfers the path computation request from PCE 1 to PCE 2 according to the PCE 1 sequence until the path computation request is transferred to PCE 3. After receiving the path computation request, PCE 3 computes a Virtual Shortest Path Tree (VSPT) that uses the destination node as a root and uses the ingress border node of autonomous system 2 as a leaf. PCE 3 sends the computation result to PCE 2. By using the computation result of PCE 3, PCE 2 computes a VSPT that uses the destination node as a root and uses the ingress border node of autonomous system 2 as a leaf. PCE 2 sends the computation result to PCE 1. By using the received computation result, PCE 1 computes the shortest path from the destination node to the source node, and sends the shortest path information to the PCC.
In the foregoing method for the PCC to obtain the shortest path information, the PCEs compute the shortest path one by one, thus making the whole computation process time-consuming.